Muscular dystrophies are inherited, progressive muscle disorders that result in severe muscle weakness, cardiomyopathy, loss of ambulation and early death. Cardiomyopathy is the cause of death in 20-30% of patients. More than 30 different genes cause muscular dystrophy with some of the most common gene mutations affecting the expression or function of the proteins of the dystrophin glycoprotein complex (DGC). Like many genetic diseases, the resulting disease phenotypes represent a combination of direct effects of the primary gene mutation on muscle and the heart, and secondary phenotypes and environmental influences that impact overall muscle and heart function. While environmental influences such as exercise are beneficial for muscle and hearts of healthy individuals, because both skeletal and cardiac muscles in dystrophic animals are sensitive to muscle injury, the impact of exercise on disease outcome and recommendations for activity in dystrophic patients are not clear. Our understanding of the mechanisms of muscular dystrophy, and many other genetic and acquired diseases, has grown considerably due to the availability of targeted mouse strains that recapitulate many important aspects of disease. State of the art approaches to study cardiovascular function in mice now rival many of the imaging and invasive catheterization methods that can be performed in humans. A mentoring portion of this proposal is to mentor the next generation of investigators in state of the art comprehensive cardiovascular phenotyping though development and execution of a series of modular, hands-on short courses and workshops to train fellows, graduate students and independent scientists. The research project portion of this proposal will take advantage state of the art radiotelemetry and cardiac phenotyping approaches to 1) genetically dissect the interplay between direct effects of loss of DGC function on the heart and the hypothesized dysfunction of the peripheral vasculature in dystrophic skeletal muscle on overall cardiovascular function and 2) Determine the molecular and physiological mechanisms of how acute and chronic exercise impact the progressive development of cardiomyopathy in dystrophic animals.